Volume 24, Number 2
2000

The Use of Gamma Rays in Book Conservation

The book conservation world has been wary of
treating infested books and documents with radiation, but sometimes
nothing works better.

Unlike its roles in medical sterilization or food disinfestation,
gamma irradiation remains far from the frontline of treatments in
the field of book conservation. Although it can be used for the
same purpose—to kill mold and other fungi, as well as
bacteria, in damaged documents—the practice of exposing valued
papers to ionizing radiation is recommended only in certain,
desperate circumstances. That said, irradiation is a young,
promising, and relatively untested treatment in the preservation
field—and as such is both scorned and lauded.

Intermittent studies performed over the past three decades have
identified the damage that irradiation can impart to paper—or,
more specifically, to cellulose, the chief component of paper.
Although paper can be produced using anything from animal furs to
metal, most paper is produced from cellulosic plant fibers, and
principally those obtained from wood pulp, cotton, and linen. During
irradiation, free radicals can be unleashed in the cellulose and
quickly react with oxygen to break cellulose molecules and degrade
the paper.

Irradiation's propensity for aging paper prematurely is borne out
in a number of studies. A 1994 European study, led by Judith Hofenk
de Graaff, compared the effects of gamma radiation and ethylene
oxide (once a standard for treating mold-infested materials) on the
aging of paper. The chemical and physical properties—such as
folding endurance, internal tearing resistance, stiffness, and pH
level—were measured on five different kinds of papers
following treatment, both before and after the paper was
artificially aged. A 10 kilogray (1 megarad) dose accelerated the
aging process in the irradiated papers by 50 to 100 percent,
depending on the paper, according to the study, while the EtO
treatment did not affect the aging of the paper. A 1998 study that
appeared in the German journal Restaurator described the effects of
increased doses of gamma rays on cellulose paper, both before and
after accelerated aging. The radiation treatment decreased
polymerization in the paper and caused it to turn yellow. A pair of
studies that appeared in the March and June 1999 issues of the
Taiwan Journal of Forest Science revealed a decrease of
up to 15 percent in the mechanical properties of the papers tested
at low to medium levels of irradiation, while at high doses the
papers showed significant decreases in brightness and increases in
yellowness.

So much for irradiation in book conservation?

In a field that strives to preserve materials, a treatment that
may incidentally degrade materials can also greatly contribute. A
slightly yellowed or embrittled document can be tolerated when the
alternative is no document at all.

"Radiation has a place, if only because all the alternatives have
their drawbacks," said Ellen McCrady, who edits the Abbey
Newsletter, which has been tracking the field of library and
archival materials preservation for 25 years. "[Conservators] know
the irradiation degrades paper and parchment, but . . . the mold and
insects will also continue to degrade the materials if they are not
killed."

"I think [irradiation] needs some open minds," said Dennis
Allsopp, a retired microbiologist and current U.K.-based consultant
who specializes in work for libraries, museums, and archives. "There
has been work done by the conservation world where, because someone
said, 'Well, we think that this actually causes a little bit of
damage,' people have written it off and said, 'Oh, we can't have
anything that causes damage.'

"Well, of course, any treatment—handling a book, fumigating
it—will probably cause some sort of damage. If you want to be
a total purist, you can just sit and watch the thing rot and weep
over it."

The Gantt Papers

The pilot project in the United States on the use of irradiation
to disinfest archival materials began in 1980 when the medical
archives of Johns Hopkins University inherited a collection of
documents from a public health officer named W. Horsley Gantt. The
materials, however, had been stored in a dilapidated row house in
Baltimore that was infested with insects, rodents, and dog and cat
carcasses. When a team of archivists first showed up at the house,
"things were strewn about—it was in total disorder," Nancy
McCall, an archivist at the JHU Alan M. Chesney Medical Archives in
Baltimore who led the effort to preserve the Gantt collection,
recalled recently. But what they found littered among the rubbish
(which also included stray car fenders and giant balls of string)
made clear that they would need to discover a way to preserve the
collection.

Dr. Gantt lived in Petrograd, Russia, in the years following the
Revolution in 1917. He had collected valuable public health
documentation, such as letters, photographs, and diaries, as well as
rare public health posters from pre-Revolution Petrograd—all
of which were found in the row house. Gantt's correspondence with
psychologist B.F. Skinner and author John Dos Passos were also
found. Most notably, Gantt's papers and letters from Russian
physiologist Ivan Pavlov were stored in the row house; Gantt was the
only American to study with Pavlov.

"Since it was a very valuable collection, we felt it was
important to make a very concerted effort to save the material, to
clean it up," McCall explained. (McCall was familiar with valuable
collections, having served as a volunteer during the devastating
flood of the Arno River in Florence in November 1966. The angeli
del fango—or "mud angels," as they were called—were
students and conservators from around the world who came to rescue
invaluable centuries-old paintings and manuscripts from the flood
waters.)

McCall and her colleagues at JHU began to contact large archival
programs, like state archives, that had larger treatment facilities.
"We were very up front about what the problems were, and that just
scared people. They didn't even want their loading docks
contaminated," McCall said.

McCall had heard of using ionizing radiation for disinfestation,
but didn't know much about it. After a search through the
literature, she found mention of its use in eastern Europe to treat
artifacts—and little else. "A lot of conservators with whom I
spoke thought it was high risk. But we felt that we had no
alternative but to take that risk." She then contacted Walter
Chappas, who was a nuclear engineer at the University of Maryland at
the time (and is now vice president and technical director for
Damilic Corporation, in Rockville, Md.), to do preliminary test
samples. Chappas performed tests using a linear accelerator to
establish dosage level and exposure time so that the extermination
process would be effective and minimize damage to paper and ink
composition.

"When you're asked to take thousands of books that may have been
published over 100 years, with different materials, different
adhesives, different printing inks," Chappas said, "the legitimate
engineer has to ask himself, 'We may kill all the bacteria, but are
we also going to damage these materials in the process?'"

After working out a plan with a commercial radiation facility,
McCall and her fellow archivists lined Paige boxes with plastic
garbage bags, packed in the papers, and sealed the boxes. In all,
295 record storage boxes of Gantt's papers were exposed to 4.5 kGy
(0.45 Mrad) of gamma radiation from a cobalt-60 source for
approximately 45 minutes. Afterward, 10 cultures produced from a
broad sampling of the irradiated materials revealed only one minor
and incidental strain of mold, which was most likely introduced when
the materials were unpacked.

"We had absolutely no problems—nothing," McCall said, and
mentioned that there have been no problems with the documents in the
nearly 20 years since the materials were placed in the Chesney
Archives. "We were severely criticized at the time by very
conservative conservators," McCall said. "But, truly, there has not
been one conservation problem."

"We never want to suggest that this is the magic wand," Chappas
explained, "and that you can take these heavily infested manuscripts
and other documents, send it through the irradiation vault, and out
the other side comes this pristine document that's clean and stable.
The fact is there's potential for problems.

"But, the good news here was that we took samples that would
otherwise have been lost. We did this technique and it not only
solved the immediate problem—killing all the bacteria [and
other contaminants]—but, in fact, did it in a way where the
long-term damage has been apparently immeasurable at this
point."

Misconceptions

The reputation of irradiation certainly suffers the same problems
among book conservators as it does most everywhere else. Namely,
people fear all things "radiation." Some people in the conservation
field quickly dismissed the technology when asked about its role in
the preservation of books, as if it were useless to discuss.

"There is the psychological point that everybody gets so scared
if they hear the word 'radiation,'" said Bert Van Zelst, director of
the Smithsonian Institution's Center for Materials Research and
Education. "That's the usual thing everywhere. But it is effective.
There's no doubt that it's effective."

If only for control of insect pests in books, using much lower
doses—0.5 kGy (0.05 Mrad)—than required for mold
disinfestation, irradiation does have an unassailable role to play
in book conservation. Looking at a higher dose level, a 1992 study
published in the German journal Restauro described the
minimal optical and mechanical effects on mold-infested historic
books at the Leipzig University Library when given 12 kGy of gamma
radiation, and noted that "severely attacked historical books showed
improved quality after having undergone the described
treatment."

"One of the problems is the scientific world and the art
world—the conservation world—have often found difficulty
in getting together," Allsopp said, "for reasons that people in them
come from very different disciplines and are trained in different
ways and mix socially in different ways."

Others expressed concerns about gamma radiation that appear to
result from hearsay rather than fact. A few mentioned the
difficulty, if not implausibility, of convincing a food or medical
irradiation facility to accept their dirty books. Ruth Garcia, a
plant operations manager for Isomedix, which operates 15 irradiation
facilities in the United States and Canada, said they readily accept
infested books, provided a number of measures are taken to package
the material to isolate the contamination.

Still others—even those in advanced positions at elite
institutions—have more troubling misconceptions. The comments
of a senior scientist at one of the world's leading conservation
institutes—who admitted irradiation was not his specialty but
goodnaturedly responded to a few questions—are telling. In
enumerating some of the disadvantages of gamma irradiation, he noted
"You have to have a reactor," which certainly would present an
obstacle if it were true.

He also said that irradiation is not needed in book conservation:
"You just keep the books dry and you have no problem."

Disaster Recovery

The only thing unusual about the late Sunday afternoon storm a
few years ago that burst over the college town of Fort Collins,
Colo., located about an hour's drive north of Denver, was the storm
itself. The summer had been unusually arid, with rainfalls totaling
less than half an inch for the region since the middle of June. Even
as low, dark clouds lingered in the foothills of the Rocky Mountains
after the storm ended—instead of clearing after dark in accord
with normal summer weather patterns—there was little
indication that the evening storm would be but a prelude to the most
intense rainfall the region had ever seen.

The clouds released a steady torrent of rain through the night,
and area residents awoke to a cool, gloomy Monday morning. By
midday, curiosity turned to concern as continued rains led to
accumulations of between 2 and 10 inches in locations in and near
Fort Collins since the previous afternoon. The creeks and ditches
were running full.

As flooding began to be reported in a nearby town, the rains had
abated across the region in the afternoon. The air, however,
remained unusually humid. Showers again erupted, and by 8:30 p.m.,
after two hours of heavy rains, the rains diminished in the east and
southeast areas of Fort Collins.

The next hour-and-a-half, however, brought accumulations of rain
over western portions of the city the likes of which had never
before been recorded. Since hourly data were first published in
1940, the campus of Colorado State University had never experienced
as much rain in a similar period as the 5.3 inches that fell between
6 p.m. and 10:30 p.m. on that Monday, July 28, 1997. Flood waters
roiled through campus, and by morning there would be 10 feet of
water in the basement of the main library.

"It's bad. It's a real mess," Camila Alire, CSU dean of
libraries, was quoted at the time in The Coloradoan.
"But the books are salvageable."

Mold can begin to form on a wet book within hours. Once it has
bloomed on an item, it will reappear whenever favorable
environmental conditions, such as high temperatures and high
humidity, allow. As such, mold can never be eradicated unless it is
killed.

Chemical treatments to kill molds in library collections are
currently discouraged because of their toxicity. Indeed, exposure
limits of ethylene oxide have been regulated to the extent that
EtO—once a mainstay for mold control—is no longer a
viable treatment option, according to Mark Gilberg, a research
coordinator at the National Center for Preservation Technology and
Training. "For me, many years it was ethylene oxide," Gilberg said.
"But the exposure limits got to the point where they were so low
that it was almost impossible to carry out."

"Ethylene oxide is the main alternative to radiation," Ellen
McCrady stated, "but we know now that it is very hard to get back
out of certain materials . . . no matter how many times the air is
purged while they are in the chamber. . . . The EtO that remains
will eventually escape from the book or document and endanger staff
and readers."

Flood ruin: The scene in the library
basement was bleak soon after the nearly 5 million gallons of water
were pumped out. The 1997 flood damaged 462,500 books, journals, and
periodicals (Photos: Colorado State University)

Other accepted treatments, such as freezing or placing the
materials in a low-oxygen environment, can be effective in limiting
the growth of molds. They do not kill the mold, but send them into
a dormant state. A cool, dry environment with plenty of air
circulation must still be maintained in the room where the
collection is stored to prevent an outbreak recurrence.

"Mold can be a very big problem depending on where you are in the
United States," Gilberg said. "It's a big problem here, down south.
. . . Mold develops. And you have to react quickly."

Within days of the Colorado University flood, work crews began
the task of removing nearly 500 000 books, periodicals, and journals
from the library. Two weeks later nearly all the books were wrapped
individually and placed into approximately 60,000 boxes. They were
then shipped on a refrigerated truck to a freezer storage facility
in Wyoming.

Pulled from the wreckage: When the floodwater was
finally pumped out of the basement of the main library at Colorado
State University, library officials were faced with restoring
damaged books such as these [Photo not published in Nuclear
News]

Meanwhile, the library was sending samples of damaged books
across campus to a microbiologist, who then tested different
treatments. "We were trying to find the easiest, safest, and
fastest way to clean and sterilize the books," said Doug Rice,
director of CSU's Environmental Quality Laboratory, who performed
the studies. "We tried several chemical methods, wet methods,
cleaning methods. We tried ozonation. And we tried cobalt-60 gamma
irradiation."

"We consulted with the Library of Congress," remembers Carmel
Bush, the library's assistant dean for technical services. "We
talked to people about what was best to do. We also had independent
physical chemistry consultants. We had a number of points of
view."

According to results published in a forthcoming book about the
library's recovery effort, gamma radiation achieved a 100 percent
reduction in mold and yeast in Rice's book samples. The next
closest reduction was 56.4 percent.

"We thought our experience and testing showed [irradiation] would
work," Bush said. "And, because we were controlling it in the
low-dosage levels, we did not expect any of the problems that could
be reported in higher doses. . . . That led us to feel that it was
a good treatment choice."

A query about irradiation posted on an Internet mailing list by a
worker from one of the library's recovery subcontractors was
answered by a SteriGenics International employee, and a plan to
irradiate nearly half-a-million books at the company's Co-60
facility in Fort Worth, Texas, was begun.

The books were taken out of cold storage and thawed. The covers
were removed and the pages were washed and shaped into a block. The
books were then freeze-dried before being shipped to the irradiation
facility in Fort Worth, where they were given an average dose of
around 15 kGy (1.5 Mrad). After irradiation, the books were further
cleaned and inspected by another recovery subcontractor in Fort
Collins. They were sent for rebinding, and then carefully again
inspected and repatriated into the library's collection.

"We're still in the process, so we haven't engaged in any
longitudinal testing," Bush said when asked about the irradiation's
noticeable effect on any books. "But we really don't expect that
there's going to be any long-term effects. Our belief is, they are
as they are, and we don't see anything relating to the radiation. I
think if we had used high-dosage irradiation, we'd be talking about
a different story, but we're not. . . .

"Mainly what [effects on the paper] we see is damage from being
underwater. The paper suffers from wrinkling, it suffers from
discoloration . . . You will see the stains where the mold was.
But, obviously, we have no active mold in it—it's completely
dead. We're real pleased about that."

Coming of Age?

For now, gamma irradiation in the preservation of books and
archival materials has been most successful in emergency
circumstances. Although the two examples provided are the only two
well-known instances in the United States in which irradiation was
used to disinfest books on a large scale, Mark Smith, director of
technical services for SteriGenics International, indicated that his
company has done similar work on collections of flood-damaged books.
He also mentioned that it is preparing to irradiate some damaged
internal documents of a major petroleum refiner.

"The trouble is, with a lot of this sort of commercial work,
people don't shout it from the rooftops," said Dennis Allsopp, who
was once president of the International Biodeterioration Society.
"This is one of the problems with biological attack on
materials—it's like people don't normally publicize their
illnesses. People don't often make a big point that they've had a
problem in their factory. They have it cured and solved, if they
can, and they're just happy that they've solved the problem."

Allsopp mentioned that it was during the Florence flood when a
largely experimental technique—now widely used—was
attempted out of necessity. "At the time . . . keeping things cold
and freezing was thought to be terribly adventurous, but it had to
be done because they just had tons of material which would have gone
rotten otherwise. And it worked."